JP2004239353A

JP2004239353A - Sealing device and bearing device for wheel with the same

Info

Publication number: JP2004239353A
Application number: JP2003029225A
Authority: JP
Inventors: Hikari Umekida; 光梅木田
Original assignee: NTN Corp; NTN Toyo Bearing Co Ltd
Current assignee: NTN Corp
Priority date: 2003-02-06
Filing date: 2003-02-06
Publication date: 2004-08-26

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing device having excellent water and dust resistances, and materializes a long seal life and low torque, and a bearing device for a wheel with the same. <P>SOLUTION: The sealing device 1 seals an annular space between an outside member 7 and inside member 4 which is relatively rotated. An elastic seal 3 is mounted onto the outside member 7 on the fixing side. A sectionally L-shaped and annular seal plate 2 opposed to the elastic seal 3 is press-fitted in the inside member 4 on the rotating side. The elastic seal 3 is provided so as to be radially outwardly inclined to a tip, and mutually separated into the inside and outside in the radial direction. The elastic seal 3 includes two side lips 6a, 6b coming into slide contact with a standing plate 2b of the seal plate 2, and a radial lip 6c coming into slide contact with the outer radial surface 4a of the inside member 4. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、防水、防塵の必要な箇所に使用される転がり軸受、特に車輪用軸受等、苛酷な環境下において所望の密封性が要求される転がり軸受の密封装置の改良に関する。
【０００２】
【従来の技術】
従来、車輪用軸受に用いられる密封装置として図４に示すようなものが用いられている。この密封装置５０は、内輪５１に嵌合されるスリンガとなるＬ字状のシール板５３と、外輪５２に取り付けられる弾性シール５４との組合せからなる。弾性シール５４は、芯金５５にゴム等の弾性体５６を一体固着したもので、２枚のサイドリップ５６ａ、５６ｂと、１枚のラジアルリップ５６ｃを備えている。
【０００３】
しかし、このように２枚のサイドリップ５６ａ、５６ａを設けると、弾性シール５４の断面高さＨが高くなるため、内外輪５１、５２間の間隔が小さくなるボール径の小さな軸受では、密封装置５０が収められないという問題があった。こうした問題を解決するものとして、図３に示すような密封装置を本出願人は提案している。
【０００４】
この密封装置６０は、シール板６１と芯金６３付き弾性シール６２とからなる。シール板６１は、円筒部６１ａの一端に外径側に延びる立板部６１ｂを有する断面Ｌ字状のものであって、内向きに円筒部６１ａで内輪５１の外径面に圧入されている。一方、弾性シール６２は、芯金６３とこの芯金６３に固着された弾性体６４とからなり、芯金６３は、外輪５２の外径面に圧入される円筒部６３ａと、その一端から外輪５２の幅面５２ａに沿って立ち下がる側板部６３ｂとからなる。
【０００５】
弾性体６４は、芯金６３の円筒部６３ａから幅方向に延出した円筒状の庇部６４ｄと、シール板６１の立板部６１ｂに摺接する２枚のサイドリップ６４ａ、６４ｂと、シール板６１の円筒部６１ａに摺接するラジアルリップ６４ｃとを有する。２枚のサイドリップ６４ａ、６４ｂは、互いに径方向の内外に離れて設けられている。また、庇部６４ｄは、その先端近傍の内周面にシール板６１の立板部６１ｂの先端が僅かな径方向隙間を介して対峙するように設けられ、この径方向隙間でラビリンスシール６５が構成されている。このような密封装置６０は、防水、防塵性に優れて軸受寿命が長く得られ、かつ内外輪間の間隔が小さくなるボール径の小さな軸受にも適用することができる（例えば、特許文献１参照。）。
【０００６】
【特許文献１】
特開２００１−１６５１７９号公報（第３、４頁、第１−３図）
【０００７】
【発明が解決しようとする課題】
しかしながら、こうした密封装置６０において、ラジアルリップ６４ｃのシールランドとなるシール板６１の円筒部６１ａは、この円筒部６１ａ自体の板厚のバラツキだけでなく、円筒部６１ａと内輪５１の外径面とのシメシロのバラツキが累積されて寸法バラツキが大きくなる。したがって、ラジアルリップ６４ｃの最小シメシロを確保しようとすると当然摩擦トルクが増大すると共に、リップ摺接部の発熱と摩耗を招来することになる。
【０００８】
本発明は、このような事情に鑑みてなされたもので、防水、防塵性に優れ、シール寿命が長く得られ、かつ低トルクの密封装置およびそれを備えた車輪用軸受装置を提供することを目的としている。
【０００９】
【課題を解決するための手段】
係る目的を達成すべく、本発明のうち請求項１に記載の発明は、相対回転する外方部材と内方部材の環状空間を密封する密封装置であって、固定側の外方部材に弾性シールを装着し、これに対向する断面Ｌ字状で環状のシール板を回転側の内方部材に圧入してなり、前記弾性シールは、先端に向かって径方向外方に傾斜し、かつ互いに径方向の内外に離れて設けられ、前記シール板の立板部に摺接する２枚のサイドリップと、前記内方部材の外径面に摺接するラジアルリップを有している構成を採用した。
【００１０】
このラジアルリップは、従来のラジアルリップのようにシール板の円筒部に摺接せず、直接内方部材の外径面に摺接しているため、この円筒部自体の板厚のバラツキだけでなく、円筒部と内方部材の外径面とのシメシロのバラツキの影響を全く受けない。したがって、シメシロのバラツキ増大に伴う摩擦トルクの増大やリップ摺接部の発熱、摩耗を防止することができる。
【００１１】
また、請求項２に記載の発明は、前記ラジアルリップの先端が、前記シール板の立板部と反対側に傾斜して延びているため、軸受内部に封入した潤滑剤の漏洩を確実に防止することができる。
【００１２】
また、請求項３に記載の発明のように、前記弾性シールが、前記シール板に対向する略Ｌ字状の芯金と、この芯金に一体固着された弾性体とからなり、前記芯金の円筒部の先端部と前記シール板の立板部の先端とが僅かな径方向隙間を介して対峙するように設けられているため、ラビリンスシールを構成して外部からの雨水やダスト等が軸受内部に浸入するのを防止することができる。
【００１３】
また、本発明のうち請求項４に記載の発明は、ハブ輪と等速自在継手と複列の転がり軸受とをユニット化し、前記ハブ輪と等速自在継手の外側継手部材とを嵌合させ、この嵌合部で、前記ハブ輪の内周面に硬化させた凹凸部を形成し、この凹凸部に前記外側継手部材の嵌合部を拡径させて食い込ませることにより、前記ハブ輪と外側継手部材とを一体に塑性結合した車輪用軸受装置において、前記外側継手部材の肩部に請求項１乃至３いずれかに記載した密封装置のシール板を圧入した構成を採用した。
【００１４】
このようなハブ輪と複列の転がり軸受と等速自在継手とを塑性結合でユニット化した第４世代構造の車輪用軸受装置において、従来、この種の車輪用軸受装置は、シール捲れ込みによる再組立は不可能となるが、このラジアルリップの捲れ込みは実質的に皆無となり、密封性の面だけでなく、組立性の面において多大なる効果がある。
【００１５】
また、請求項５に記載の発明のように、前記複列の転がり軸受における内側転走面のうち一方を前記ハブ輪に、他方を前記外側継手部材にそれぞれ形成すれば、車輪用軸受装置の部品点数を最小限に止め、究極のコンパクト化を図ることができる。
【００１６】
【発明の実施の形態】
以下、本発明の実施の形態を図面に基づいて詳細に説明する。図１は、本発明に係る密封装置の実施形態を示す縦断面図である。
【００１７】
この密封装置１は、シール板２と弾性シール３とを備えている。シール板２は、円筒部２ａの一端に外径側に延びる立板部２ｂを有する断面Ｌ字状に形成され、内向きに円筒部２ａで内方部材４の外径面４ａに圧入されている。一方、弾性シール３は、芯金５とこの芯金５に固着された弾性体６とからなり、芯金５は、外方部材７の端部内径面に圧入される円筒部５ａと、その一端から径方向内方に延びる側板部５ｂを有する断面略Ｌ字状に形成されている。
【００１８】
弾性体６は、芯金５の内周面および円筒部５ａの先端部を覆うように設けられ、シール板２の立板部２ｂに摺接する２枚のサイドリップ６ａ、６ｂと、内方部材４の外径面４ａに直接摺接するラジアルリップ６ｃとを有する。２枚のサイドリップ６ａ、６ｂは、先端に向かって径方向外方に傾斜し、かつ互いに径方向の内外に離れて設けられている。これら２枚のサイドリップ６ａ、６ｂは略同一の形状に形成され、シール板２の立板部２ｂに対して所定のシメシロで摺接している。芯金５の円筒部５ａは、その先端部に固着された弾性体６とシール板２の立板部２ｂの先端とが僅かな径方向隙間を介して対峙するように設けられ、この径方向隙間でラビリンスシール８が構成されている。このラビリンスシール８を通過した雨水やダストは、外径側のサイドリップ６ａで形成される略Ｕ字状の環状空間に浸入するが、内方部材４の回転に伴う遠心力によって外部に排出される。また、車両が停止中で、内方部材４が回転していなくとも、この環状空間が所謂樋の役目をなし、雨水やダストはこの環状空間に滞留することなく下方に垂れ落ち、その後内方部材４の回転に伴って外部に排出される。したがって、リップ摺接部から雨水やダストが容易に内部に浸入するのを防止することができる。そして、例え外径側のサイドリップ６ａの摺接部から微量の雨水やダストが浸入したとしても、内径側のサイドリップ６ｂにより阻止することができるため、立板部２ｂとのシメシロを増大することなく、防水、防塵性を可及的に向上させることができる。
【００１９】
なお、シール性の面からサイドリップ６ａ、６ｂのシメシロは大きい方が好ましいが、シメシロが大きくなれば摩擦トルクも大きくなり、発熱や摩耗の面で問題が生じる。本実施形態では、例えば、外径側のサイドリップ６ａを内径側のサイドリップ６ｂより僅かに長くすることにより、２枚のサイドリップ６ａ、６ｂのシメシロを異ならせ、摩擦トルクを調整することができる。
【００２０】
ラジアルリップ６ｃは、内方部材４の外径面４ａに対して略３０度の角度で摺接し、軸受内部に封入した潤滑剤の漏洩を主に防止している。このラジアルリップ６ｃは、従来のラジアルリップのようにシール板２の円筒部２ａに摺接せず、直接内方部材４の外径面４ａに摺接しているため、この円筒部２ａ自体の板厚のバラツキだけでなく、円筒部２ａと内方部材４の外径面４ａとのシメシロのバラツキの影響を全く受けない。したがって、シメシロ増大に伴う摩擦トルクの増大やリップ摺接部の発熱、摩耗を防止することができる。
【００２１】
また、弾性シール３の断面高さをボール等の転動体サイズに関わらず、２枚のサイドリップ６ａ、６ｂが干渉しない最適なリップ間隔を確保することができ、防水、防塵性に優れた長寿命の密封装置を提供することができる。
【００２２】
さらに、この種のスリンガタイプの組合せシールにおいては、スリンガとなるシール板２の円筒部２ａと内方部材４の外径面４ａとの嵌合面からの雨水やダスト等の浸入も否めないため、シール板２の円筒部２ａを内方部材４の外径面４ａに圧入して使用されるのが一般的である。ところが、圧入をよりタイトにすることによりシール板２の円筒部２ａだけでなく、２枚のサイドリップ６ａ、６ｂの摺接面となる立板部２ｂまでその変形が及び、良好な密封性が確保できないと言った問題も散在していた。したがって、嵌合部となるシール板２の円筒部２ａの内径面、および内方部材４の外径面４ａの寸法管理と共に、真円度等の形状についても厳しく規制する必要があった。本実施形態では、シール板２の円筒部２ａを内方部材４の外径面４ａに直接摺接させるようにしたので、従来のような厳しい寸法、形状管理が不要となり、内方部材４の外径面４ａの寸法と面粗さを管理するだけでシール板２の円筒部２ａと内方部材４の外径面４ａとの嵌合面からの雨水等の浸入を防止することができる。
【００２３】
図２は、本発明に係る車輪用軸受装置の実施形態を示す縦断面図である。この車輪用軸受装置は、前述した密封装置を備え、ハブ輪と複列の転がり軸受と等速自在継手とをユニット化して構成している。なお、以下の説明では、車両に組み付けた状態で、車両の外側寄りとなる側（図面左側）をアウトボード側、中央寄り側をインボード側（図面右側）という。
【００２４】
ハブ輪９は、アウトボード側の端部に車輪（図示せず）を取り付けるための車輪取付フランジ１０を一体に有している。ハブ輪９の内周面には凹凸部１１が形成され、熱処理によって表面硬さを５４〜６４ＨＲＣの範囲に硬化層が形成されている（図中散点模様にて示す）。熱処理としては、局部加熱ができ、硬化層深さの設定が比較的容易にできる高周波誘導加熱による焼入れが好適である。
【００２５】
なお、凹凸部１１は、複数列の軸方向溝と独立した環状溝とからなる溝を直交させてアヤメローレット状を形成している。凹凸部１１の凸部は良好な食い込み性を確保するために三角形状等の尖端形状に形成されている。なお、凹凸部は互いに傾斜した螺旋溝からなる交叉溝のようなものであっても良い。
【００２６】
複列の転がり軸受１２は、外方部材７と内方部材１３と複列の転動体１４、１４とを備え、外方部材７は外周に車体（図示せず）に取り付けるための車体取付フランジ７ａを一体に有し、内周には複列の外側転走面７ｂ、７ｂが形成されている。一方、内方部材１３は、ハブ輪９と後述する外側継手部材１８を指し、外方部材７の外側転走面７ｂ、７ｂに対向するアウトボード側の内側転走面９ａがハブ輪９の外周に、インボード側の内側転走面１８ａが外側継手部材１８の外周にそれぞれ形成されている。複列の転動体１４、１４がこれら転走面７ｂ、９ａと７ｂ、１８ａ間にそれぞれ収容され、保持器１５、１５で転動自在に保持されている。複列の転がり軸受１２の端部には密封装置１、１６が装着され、軸受内部に封入した潤滑グリースの漏洩と、外部からの雨水やダスト等の浸入を防止している。なお、アウトボード側の密封装置１６をインボード側と同様の密封装置１としても良い。
【００２７】
ハブ輪９の外周において、密封装置１６のシールリップが摺接するシールランド部、内側転走面９ａ、および外側継手部材１８の肩部２０と当接するインロウ部９ｂの表面に高周波焼入れによって硬化層を形成している（図中散点模様にて示す）。ここで複列の転がり軸受１２は転動体１４、１４をボールとした複列アンギュラ玉軸受を例示したが、これに限らず転動体に円すいころを使用した複列円すいころ軸受であっても良い。
【００２８】
等速自在継手１７は外側継手部材１８と図示しない継手内輪、ケージ、およびトルク伝達ボールとからなる。外側継手部材１８はカップ状のマウス部１９と、このマウス部１９の底部をなす肩部２０と、この肩部２０から軸方向に延びる軸部２１を有し、マウス部１９の内周には軸方向に延びる曲線状のトラック溝１９ａが形成されている。
【００２９】
外側継手部材１８の肩部２０の外周には前述した内側転走面１８ａが形成され、軸部２１は小径段部２１ａと嵌合部２１ｂを有し、中空に形成されている。ここで、外方部材７に前述した保持器１５で保持された複列の転動体１４、１４、およびアウトボード側の密封装置１６とインボード側の密封装置１の弾性シール３を予め組込む。そして外側継手部材１８の肩部２０の外径面に前述したシール板２の円筒部２ａを圧入した状態で、ハブ輪９のインロウ部９ｂと外側継手部材１８の肩部２０とが突合されるように軸部２１がハブ輪９に内嵌される。その後、嵌合部２１ｂの内径にマンドレル等の加締治具を挿入・抜脱させる等、適宜な手段で嵌合部２１ｂを拡径してハブ輪９の凹凸部１１に食い込ませ、ハブ輪９と外側継手部材１８とを塑性結合させる。
【００３０】
これにより、この結合部はトルク伝達手段と、ハブ輪９と外側継手部材１８の結合手段とを併せ持つため、従来のセレーション等のトルク伝達手段をハブ輪９や外側継手部材１８に形成する必要はなく、また、締結ナット等の固定手段も不要となるため、装置の一層の軽量・コンパクト化を実現することができる。
【００３１】
外側継手部材１８において、マウス部１９の内周に形成したトラック溝１９ａと密封装置１が嵌合される外径面から転走面１８ａ、および小径段部２１ａに亙って表面硬化処理を施す。硬化処理として高周波誘導加熱による焼入れが好適である。また、拡径する嵌合部２１ｂは、鍛造後の素材表面硬さ２４ＨＲＣ以下の未焼入れ部とし、前述したハブ輪９の凹凸部１１の表面硬さ５４〜６４ＨＲＣとの硬度差を３０ＨＲＣ以上に設定するのが好ましい。これにより、嵌合部２１ｂが凹凸部１１に容易に、かつ深く食い込み、凹凸部１１の先端が潰れることなく強固に両者を塑性結合することができる。なお、中空状の外側継手部材１８およびハブ輪９の内径にエンドキャップ２２、２３を装着して、マウス部１９に封入された潤滑グリースの外部への漏洩と外部からのダスト浸入を防止している。
【００３２】
従来、予め外側継手部材の肩部にシール板の円筒部を圧入した状態で、弾性シールの内径に挿入しようとすると、ラジアルリップの先端とシール板の円筒部が干渉し、ラジアルリップが捲れ込むと言った問題が発生していた。ラジアルリップのシメシロが大きければ大きい程その傾向が強く、ラジアルリップの先端形状やシール板の円筒部の端部形状に特殊な細工を施すと共に、組立に際しては細心の配慮が必要であった。特にこうしたハブ輪９と複列の転がり軸受１２と等速自在継手１７とを塑性結合でユニット化した第４世代構造の車輪用軸受装置においては、シール捲れ込みによる再組立は不可能となる。したがって、前述したように本発明に係る密封装置１では、このラジアルリップ６ｃの捲れ込みは実質的に皆無となり、これを適用する効果は密封性の面だけでなく、組立性の面において多大なるものがある。
【００３３】
以上、本発明の実施の形態について説明を行ったが、本発明はこうした実施の形態に何等限定されるものではなく、あくまで例示であって、本発明の要旨を逸脱しない範囲内において、さらに種々なる形態で実施し得ることは勿論のことであり、本発明の範囲は、特許請求の範囲の記載によって示され、さらに特許請求の範囲に記載の均等の意味、および範囲内のすべての変更を含む。
【００３４】
【発明の効果】
以上詳述したように、本発明に係る密封装置は、相対回転する外方部材と内方部材の環状空間を密封する密封装置であって、固定側の外方部材に弾性シールを装着し、これに対向する断面Ｌ字状で環状のシール板を回転側の内方部材に圧入してなり、前記弾性シールは、先端に向かって径方向外方に傾斜し、かつ互いに径方向の内外に離れて設けられ、前記シール板の立板部に摺接する２枚のサイドリップと、前記内方部材の外径面に摺接するラジアルリップを有しているので、シール板の円筒部自体の板厚のバラツキだけでなく、円筒部と内方部材の外径面とのシメシロのバラツキの影響を受けない。したがって、シメシロ増大に伴う摩擦トルクの増大やリップ摺接部の発熱、摩耗を防止することができる。また、弾性シールの断面高さをボール等の転動体サイズに関わらず、２枚のサイドリップが干渉しない最適なリップ間隔を確保することができ、防水、防塵性に優れた長寿命の密封装置を提供することができる。さらに、シール板と内方部材は、従来のような厳しい寸法、形状管理が不要となり、内方部材の外径面の面粗さを管理するだけでシール板の円筒部と内方部材の外径面との嵌合面からの雨水等の浸入を防止することができる。
【００３５】
また、本発明に係る車輪用軸受装置は、ハブ輪と等速自在継手と複列の転がり軸受とをユニット化し、前記ハブ輪と等速自在継手の外側継手部材とを嵌合させ、この嵌合部で、前記ハブ輪の内周面に硬化させた凹凸部を形成し、この凹凸部に前記外側継手部材の嵌合部を拡径させて食い込ませることにより、前記ハブ輪と外側継手部材とを一体に塑性結合した車輪用軸受装置において、前記外側継手部材の肩部に本発明に係る密封装置のシール板を圧入したので、ハブ輪と複列の転がり軸受と等速自在継手とを塑性結合でユニット化した第４世代構造の車輪用軸受装置において、従来、シール捲れ込みによる再組立は不可能となるが、このラジアルリップの捲れ込みは実質的に皆無となり、このような非分離タイプの第４世代構造の車輪用軸受装置に前述した密封装置を適用することは、密封性の面だけでなく組立性の面において多大なる効果がある。
【図面の簡単な説明】
【図１】本発明に係る密封装置の実施形態を示す縦断面図である。
【図２】本発明に係る車輪用軸受装置の実施形態を示す縦断面図である。
【図３】従来の密封装置を示す縦断面図である。
【図４】同上。
【符号の説明】
１、１６・・・・・・・・・・・・・・・・密封装置
２・・・・・・・・・・・・・・・・・・・シール板
２ａ・・・・・・・・・・・・・・・・・・円筒部
２ｂ・・・・・・・・・・・・・・・・・・立板部
３・・・・・・・・・・・・・・・・・・・弾性シール
４・・・・・・・・・・・・・・・・・・・内方部材
４ａ・・・・・・・・・・・・・・・・・・外径面
５・・・・・・・・・・・・・・・・・・・芯金
５ａ・・・・・・・・・・・・・・・・・・円筒部
５ｂ・・・・・・・・・・・・・・・・・・側板部
６・・・・・・・・・・・・・・・・・・・弾性体
６ａ、６ｂ・・・・・・・・・・・・・・・サイドリップ
６ｃ・・・・・・・・・・・・・・・・・・ラジアルリップ
７・・・・・・・・・・・・・・・・・・・外方部材
７ａ・・・・・・・・・・・・・・・・・・車体取付フランジ
７ｂ・・・・・・・・・・・・・・・・・・外側転走面
８・・・・・・・・・・・・・・・・・・・ラビリンスシール
９・・・・・・・・・・・・・・・・・・・ハブ輪
１０・・・・・・・・・・・・・・・・・・車輪取付フランジ
１１・・・・・・・・・・・・・・・・・・凹凸部
１２・・・・・・・・・・・・・・・・・・複列の転がり軸受
１３・・・・・・・・・・・・・・・・・・内方部材
１４・・・・・・・・・・・・・・・・・・転動体
１５・・・・・・・・・・・・・・・・・・保持器
１７・・・・・・・・・・・・・・・・・・等速自在継手
１８・・・・・・・・・・・・・・・・・・外側継手部材
１９・・・・・・・・・・・・・・・・・・マウス部
１９ａ・・・・・・・・・・・・・・・・・トラック溝
２０・・・・・・・・・・・・・・・・・・肩部
２１・・・・・・・・・・・・・・・・・・軸部
２１ａ・・・・・・・・・・・・・・・・・小径段部
２１ｂ・・・・・・・・・・・・・・・・・嵌合部
２２、２３・・・・・・・・・・・・・・・エンドキャップ
５０、６０・・・・・・・・・・・・・・・密封装置
５１・・・・・・・・・・・・・・・・・・内輪
５２・・・・・・・・・・・・・・・・・・外輪
５２ａ・・・・・・・・・・・・・・・・・幅面
５３、６１・・・・・・・・・・・・・・・シール板
５４、６２・・・・・・・・・・・・・・・弾性シール
５５、６３・・・・・・・・・・・・・・・芯金
５６、６４・・・・・・・・・・・・・・・弾性体
５６ａ、５６ｂ、６４ａ、６４ｂ・・・・・サイドリップ
５６ｃ、６４ｃ・・・・・・・・・・・・・ラジアルリップ
６１ａ・・・・・・・・・・・・・・・・・円筒部
６１ｂ・・・・・・・・・・・・・・・・・立板部
６３ａ・・・・・・・・・・・・・・・・・円筒部
６３ｂ・・・・・・・・・・・・・・・・・側板部
６４ｄ・・・・・・・・・・・・・・・・・庇部
６５・・・・・・・・・・・・・・・・・・ラビリンスシール
Ｈ・・・・・・・・・・・・・・・・・・・断面高さ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement in a sealing device for a rolling bearing which is required to have a desired sealing property in a severe environment such as a rolling bearing used in a place where waterproof and dustproof is required, particularly a wheel bearing.
[0002]
[Prior art]
Conventionally, a sealing device as shown in FIG. 4 has been used for a wheel bearing. The sealing device 50 includes a combination of an L-shaped seal plate 53 serving as a slinger fitted to the inner ring 51 and an elastic seal 54 attached to the outer ring 52. The elastic seal 54 is formed by integrally fixing an elastic body 56 such as rubber to a cored bar 55, and includes two side lips 56a and 56b and one radial lip 56c.
[0003]
However, when the two side lips 56a, 56a are provided in this manner, the cross-sectional height H of the elastic seal 54 increases, so that in a bearing having a small ball diameter in which the distance between the inner and outer rings 51, 52 is reduced, the sealing device is used. There was a problem that 50 could not be stored. To solve such a problem, the present applicant has proposed a sealing device as shown in FIG.
[0004]
The sealing device 60 includes a seal plate 61 and an elastic seal 62 with a core bar 63. The seal plate 61 has an L-shaped cross section having an upright plate portion 61b extending to the outer diameter side at one end of the cylindrical portion 61a, and is press-fitted inward to the outer diameter surface of the inner ring 51 at the cylindrical portion 61a. . On the other hand, the elastic seal 62 includes a metal core 63 and an elastic body 64 fixed to the metal core 63. The metal core 63 has a cylindrical portion 63 a press-fitted into the outer diameter surface of the outer race 52, and an outer race from one end thereof. 52 and a side plate 63b that falls along the width surface 52a.
[0005]
The elastic body 64 includes a cylindrical eave portion 64d extending in the width direction from the cylindrical portion 63a of the cored bar 63, two side lips 64a and 64b slidingly contacting the upright plate portion 61b of the seal plate 61, and a seal plate. And a radial lip 64c that is in sliding contact with the cylindrical portion 61a. The two side lips 64a and 64b are provided apart from each other in and out in the radial direction. The eave portion 64d is provided on the inner peripheral surface near the tip so that the tip of the standing plate portion 61b of the seal plate 61 faces through a small radial gap, and the labyrinth seal 65 is formed by the radial gap. It is configured. Such a sealing device 60 is excellent in waterproofness and dustproofness, has a long bearing life, and can be applied to a small-diameter bearing in which the distance between the inner and outer rings is small (for example, see Patent Document 1). .).
[0006]
[Patent Document 1]
JP-A-2001-165179 (pages 3 and 4, FIG. 1-3)
[0007]
[Problems to be solved by the invention]
However, in such a sealing device 60, the cylindrical portion 61a of the seal plate 61 serving as the seal land of the radial lip 64c has not only the thickness variation of the cylindrical portion 61a itself, but also the outer diameter surface of the cylindrical portion 61a and the inner ring 51. And the dimensional variation increases. Therefore, if an attempt is made to secure the minimum squeeze of the radial lip 64c, the friction torque naturally increases, and the lip sliding contact portion generates heat and wears.
[0008]
The present invention has been made in view of such circumstances, and provides a sealing device with excellent waterproof and dustproof properties, a long sealing life, a low torque, and a wheel bearing device having the same. The purpose is.
[0009]
[Means for Solving the Problems]
In order to achieve the object, an invention according to claim 1 of the present invention is a sealing device for sealing an annular space between an outer member and an inner member that rotate relative to each other, wherein the outer member on the fixed side has an elasticity. A seal is mounted, and an annular seal plate having an L-shaped cross section facing the seal is pressed into the inner member on the rotation side, and the elastic seals are inclined radially outward toward the distal end, and A configuration is employed in which two side lips are provided radially inward and outward and are in sliding contact with the standing plate portion of the seal plate, and radial lips are in sliding contact with the outer diameter surface of the inner member.
[0010]
This radial lip does not slide on the cylindrical portion of the seal plate as in the conventional radial lip, but directly slides on the outer diameter surface of the inner member. In addition, there is no influence of the variation in the squeezing between the cylindrical portion and the outer diameter surface of the inner member. Accordingly, it is possible to prevent an increase in friction torque and an increase in heat generation and abrasion of the lip sliding contact portion due to an increase in unevenness of the squeeze.
[0011]
In the invention according to claim 2, the tip of the radial lip extends obliquely to the side opposite to the upright portion of the seal plate, so that leakage of the lubricant sealed inside the bearing is reliably prevented. can do.
[0012]
According to a third aspect of the present invention, the elastic seal includes a substantially L-shaped metal core facing the seal plate, and an elastic body integrally fixed to the metal core. Since the tip of the cylindrical portion and the tip of the upright portion of the seal plate are provided so as to face each other through a slight radial gap, a labyrinth seal is formed to prevent rainwater and dust from the outside. It can be prevented from entering the inside of the bearing.
[0013]
In the invention according to claim 4 of the present invention, the hub wheel, the constant velocity universal joint, and the double row rolling bearing are unitized, and the hub wheel and the outer joint member of the constant velocity universal joint are fitted. By forming a hardened uneven portion on the inner peripheral surface of the hub wheel at the fitting portion, and expanding the fitting portion of the outer joint member into the uneven portion so as to bite the hub wheel, In the wheel bearing device in which the outer joint member is integrally and plastically connected, a seal plate of the sealing device according to any one of claims 1 to 3 is press-fitted into a shoulder of the outer joint member.
[0014]
In such a fourth-generation wheel bearing device in which a hub wheel, a double-row rolling bearing, and a constant velocity universal joint are united by plastic coupling, this type of wheel bearing device has heretofore been manufactured by sealing up. Although reassembly is not possible, this radial lip is substantially free of entanglement, which has a great effect not only on the sealing property but also on the assembling property.
[0015]
Further, as in the invention according to claim 5, if one of the inner rolling surfaces in the double row rolling bearing is formed on the hub wheel and the other is formed on the outer joint member, respectively, The number of parts can be kept to a minimum and ultimate compactness can be achieved.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an embodiment of the sealing device according to the present invention.
[0017]
The sealing device 1 includes a seal plate 2 and an elastic seal 3. The seal plate 2 is formed in an L-shaped cross section having an upright plate portion 2b extending to the outer diameter side at one end of the cylindrical portion 2a, and is pressed inward into the outer diameter surface 4a of the inner member 4 by the cylindrical portion 2a. I have. On the other hand, the elastic seal 3 includes a metal core 5 and an elastic body 6 fixed to the metal core 5, and the metal core 5 has a cylindrical portion 5 a which is pressed into the inner diameter surface of the end of the outer member 7, It is formed in a substantially L-shaped section having a side plate portion 5b extending radially inward from one end.
[0018]
The elastic body 6 is provided so as to cover the inner peripheral surface of the cored bar 5 and the tip of the cylindrical portion 5a, and has two side lips 6a and 6b slidingly contacting the upright plate portion 2b of the seal plate 2, and an inner member. 4 has a radial lip 6c directly in sliding contact with the outer diameter surface 4a. The two side lips 6a, 6b are inclined radially outward toward the distal end, and are provided apart from each other radially inward and outward. These two side lips 6a and 6b are formed in substantially the same shape, and are in sliding contact with the upright plate portion 2b of the seal plate 2 with a predetermined squeeze. The cylindrical portion 5a of the cored bar 5 is provided such that the elastic body 6 fixed to the distal end portion thereof and the distal end of the standing plate portion 2b of the seal plate 2 face each other through a slight radial gap. The labyrinth seal 8 is constituted by the gap. Rainwater and dust that have passed through the labyrinth seal 8 penetrate into a substantially U-shaped annular space formed by the outer lip side lip 6 a, but are discharged to the outside by centrifugal force caused by rotation of the inner member 4. You. Further, even when the vehicle is stopped and the inner member 4 is not rotating, the annular space serves as a so-called gutter, and rainwater and dust droop downward without staying in the annular space. It is discharged to the outside as the member 4 rotates. Therefore, it is possible to prevent rainwater or dust from easily entering the inside from the lip sliding contact portion. Even if a small amount of rainwater or dust enters from the sliding portion of the outer side lip 6a, it can be blocked by the inner side lip 6b, so that the amount of squeezing with the standing plate portion 2b is increased. The waterproof and dustproof properties can be improved as much as possible.
[0019]
It is preferable that the side lips 6a and 6b have a large squeeze from the viewpoint of the sealing performance. However, if the sise shiro is large, the friction torque is also increased, which causes a problem in terms of heat generation and wear. In the present embodiment, for example, by making the outer lip side lip 6a slightly longer than the inner lip side lip 6b, the two side lips 6a and 6b can have different squeeze rolls to adjust the friction torque. it can.
[0020]
The radial lip 6c is in sliding contact with the outer diameter surface 4a of the inner member 4 at an angle of approximately 30 degrees, and mainly prevents leakage of the lubricant sealed inside the bearing. Unlike the conventional radial lip, the radial lip 6c does not slide on the cylindrical portion 2a of the seal plate 2 but slides directly on the outer diameter surface 4a of the inner member 4, so that the plate of the cylindrical portion 2a itself is formed. In addition to the thickness variation, there is no influence from the variation in the squeezing between the cylindrical portion 2a and the outer diameter surface 4a of the inner member 4. Therefore, it is possible to prevent an increase in friction torque and an increase in heat generation and wear in the lip sliding contact portion due to an increase in squeezing.
[0021]
Also, regardless of the cross-sectional height of the elastic seal 3, regardless of the size of the rolling element such as a ball, an optimal lip interval where the two side lips 6a and 6b do not interfere with each other can be ensured. A long life sealing device can be provided.
[0022]
Furthermore, in this type of slinger-type combination seal, it is undeniable that rainwater, dust, and the like intrude from the fitting surface between the cylindrical portion 2a of the seal plate 2 serving as the slinger and the outer diameter surface 4a of the inner member 4. In general, the cylindrical portion 2a of the seal plate 2 is press-fitted into the outer diameter surface 4a of the inner member 4 for use. However, by making the press fit tighter, not only the cylindrical portion 2a of the seal plate 2 but also the upright plate portion 2b serving as a sliding contact surface of the two side lips 6a, 6b is deformed, and good sealing performance is obtained. There were scattered problems saying they could not secure them. Accordingly, it is necessary to control the dimensions of the inner diameter surface of the cylindrical portion 2a of the seal plate 2 serving as the fitting portion and the outer diameter surface 4a of the inner member 4, and also strictly regulate the shape such as roundness. In the present embodiment, the cylindrical portion 2a of the seal plate 2 is brought into direct sliding contact with the outer diameter surface 4a of the inner member 4. It is possible to prevent infiltration of rainwater or the like from the fitting surface between the cylindrical portion 2a of the seal plate 2 and the outer diameter surface 4a of the inner member 4 only by managing the dimensions and the surface roughness of the outer diameter surface 4a.
[0023]
FIG. 2 is a longitudinal sectional view showing an embodiment of the wheel bearing device according to the present invention. This wheel bearing device includes the above-described sealing device, and is configured by unitizing a hub wheel, a double-row rolling bearing, and a constant velocity universal joint. In the following description, a side closer to the outside of the vehicle (left side in the drawing) and a center side are referred to as an inboard side (right side in the drawing) in a state where the vehicle is assembled.
[0024]
The hub wheel 9 integrally has a wheel mounting flange 10 for mounting a wheel (not shown) at an end on the outboard side. An uneven portion 11 is formed on the inner peripheral surface of the hub wheel 9, and a hardened layer is formed by heat treatment to have a surface hardness in the range of 54 to 64 HRC (indicated by a dotted pattern in the figure). As the heat treatment, quenching by high-frequency induction heating that can perform local heating and relatively easily set the depth of the hardened layer is preferable.
[0025]
In addition, the uneven portion 11 is formed in an iris knurled shape by orthogonally intersecting grooves formed of a plurality of rows of axial grooves and independent annular grooves. The protruding portion of the uneven portion 11 is formed in a pointed shape such as a triangular shape in order to secure a good biting property. In addition, the uneven portion may be like a cross groove composed of spiral grooves that are inclined with respect to each other.
[0026]
The double-row rolling bearing 12 includes an outer member 7, an inner member 13, and double-row rolling elements 14, 14, and the outer member 7 is provided on the outer periphery with a vehicle body mounting flange for mounting to a vehicle body (not shown). 7a, and multiple rows of outer rolling surfaces 7b, 7b are formed on the inner periphery. On the other hand, the inner member 13 refers to the hub wheel 9 and an outer joint member 18 described later, and the inner rolling surface 9a on the outboard side facing the outer rolling surfaces 7b, 7b of the outer member 7 is On the outer periphery, an inner rolling surface 18 a on the inboard side is formed on the outer periphery of the outer joint member 18. Double rows of rolling elements 14 are accommodated between these rolling surfaces 7b, 9a and 7b, 18a, respectively, and are held by rollers 15, 15 so as to be able to roll freely. Sealing devices 1 and 16 are attached to the ends of the double row rolling bearings 12 to prevent leakage of lubricating grease sealed inside the bearings and intrusion of rainwater and dust from the outside. The sealing device 16 on the outboard side may be the same as the sealing device 1 on the inboard side.
[0027]
On the outer periphery of the hub wheel 9, a hardened layer is hardened by induction hardening on the surfaces of the seal land portion, the inner rolling surface 9 a, and the shoulder portion 20 b of the outer joint member 18, which are in contact with the seal lip of the sealing device 16. (Shown by dotted patterns in the figure). Here, the double-row rolling bearing 12 is exemplified by a double-row angular contact ball bearing using the rolling elements 14 and 14 as balls, but is not limited to this, and may be a double-row tapered roller bearing using tapered rollers for the rolling elements. .
[0028]
The constant velocity universal joint 17 includes an outer joint member 18, a joint inner ring (not shown), a cage, and a torque transmitting ball. The outer joint member 18 has a cup-shaped mouth portion 19, a shoulder portion 20 forming the bottom of the mouth portion 19, and a shaft portion 21 extending in the axial direction from the shoulder portion 20. A curved track groove 19a extending in the axial direction is formed.
[0029]
The inner rolling surface 18a described above is formed on the outer periphery of the shoulder portion 20 of the outer joint member 18, and the shaft portion 21 has a small-diameter stepped portion 21a and a fitting portion 21b, and is formed hollow. Here, the double-row rolling elements 14 and 14 held by the retainer 15 and the elastic seals 3 of the outboard-side sealing device 16 and the inboard-side sealing device 1 are previously assembled in the outer member 7. Then, with the aforementioned cylindrical portion 2a of the seal plate 2 pressed into the outer diameter surface of the shoulder portion 20 of the outer joint member 18, the spigot portion 9b of the hub wheel 9 and the shoulder portion 20 of the outer joint member 18 are butted. Shaft portion 21 is fitted inside hub wheel 9 as described above. Thereafter, the fitting portion 21b is enlarged in diameter by an appropriate means such as inserting and removing a caulking jig such as a mandrel into and out of the inside diameter of the fitting portion 21b, and is caused to bite into the concave and convex portion 11 of the hub wheel 9, thereby forming the hub wheel. 9 and the outer joint member 18 are plastically connected.
[0030]
As a result, since this coupling portion has both the torque transmitting means and the coupling means for connecting the hub wheel 9 and the outer joint member 18, it is not necessary to form a conventional torque transmitting means such as serrations on the hub wheel 9 and the outer joint member 18. In addition, since a fixing means such as a fastening nut is not required, it is possible to further reduce the weight and size of the device.
[0031]
In the outer joint member 18, a surface hardening process is performed from the outer diameter surface where the sealing device 1 is fitted to the track groove 19a formed on the inner periphery of the mouth portion 19 to the rolling surface 18a and the small diameter step portion 21a. . Quenching by high-frequency induction heating is preferred as the curing treatment. The fitting portion 21b to be expanded in diameter is an unquenched portion having a surface hardness of 24 HRC or less after forging, and the hardness difference between the surface hardness 54 to 64 HRC of the above-described uneven portion 11 of the hub wheel 9 is 30 HRC or more. It is preferable to set. Accordingly, the fitting portion 21b can easily and deeply bite into the uneven portion 11, and the two can be firmly plastically connected without the tip of the uneven portion 11 being crushed. In addition, end caps 22 and 23 are attached to the inner diameter of the hollow outer joint member 18 and the inner diameter of the hub wheel 9 to prevent the lubricating grease sealed in the mouth portion 19 from leaking outside and infiltrating dust from outside. I have.
[0032]
Conventionally, when the cylindrical portion of the seal plate is press-fitted into the shoulder portion of the outer joint member in advance, when trying to insert it into the inner diameter of the elastic seal, the tip of the radial lip and the cylindrical portion of the seal plate interfere with each other, and the radial lip is rolled up The problem was said. The larger the radial lip width, the greater the tendency. The special shape is required for the tip shape of the radial lip and the end portion of the cylindrical portion of the seal plate, and close attention must be paid to the assembly. In particular, in such a fourth-generation wheel bearing device in which the hub wheel 9, the double-row rolling bearing 12 and the constant velocity universal joint 17 are united by plastic coupling, reassembly by rolling in the seal becomes impossible. Therefore, as described above, in the sealing device 1 according to the present invention, the radial lip 6c is substantially free from being rolled up, and the effect of applying the radial lip 6c is great not only in the sealing performance but also in the assembling performance. There is something.
[0033]
As described above, the embodiments of the present invention have been described. However, the present invention is not limited to these embodiments at all, but is merely an example, and may be variously modified without departing from the gist of the present invention. The scope of the present invention is, of course, indicated by the appended claims, and further includes the equivalent meanings described in the appended claims and all modifications within the scope. Including.
[0034]
【The invention's effect】
As described in detail above, the sealing device according to the present invention is a sealing device that seals the annular space between the outer member and the inner member that rotate relative to each other, and attaches an elastic seal to the outer member on the fixed side, An annular seal plate having an L-shaped cross section opposed thereto is press-fitted into the inner member on the rotating side, and the elastic seals are inclined radially outward toward the distal end and radially inward and outward relative to each other. Since there are two side lips which are provided apart and are in sliding contact with the upright portion of the seal plate, and a radial lip is in sliding contact with the outer diameter surface of the inner member, the plate of the cylindrical portion itself of the seal plate is provided. It is not affected by not only the thickness variation but also the variation of the squeezing between the cylindrical portion and the outer diameter surface of the inner member. Therefore, it is possible to prevent an increase in friction torque and an increase in heat generation and wear in the lip sliding contact portion due to an increase in squeezing. Also, regardless of the size of the rolling element such as a ball, the cross-section height of the elastic seal can secure an optimum lip interval where two side lips do not interfere with each other. Can be provided. Furthermore, the strict size and shape control of the seal plate and the inner member as in the related art are not required, and the outer peripheral surface of the seal plate and the inner member are merely controlled by controlling the surface roughness of the outer diameter surface of the inner member. It is possible to prevent infiltration of rainwater or the like from the fitting surface with the radial surface.
[0035]
Further, the bearing device for a wheel according to the present invention, a hub wheel, a constant velocity universal joint, and a double row rolling bearing are unitized, and the hub wheel and an outer joint member of the constant velocity universal joint are fitted to each other. At the joint portion, a hardened uneven portion is formed on the inner peripheral surface of the hub wheel, and the fitting portion of the outer joint member is enlarged and bitten into the uneven portion, thereby forming the hub wheel and the outer joint member. In the bearing device for a wheel, which is plastically integrated with the above, the seal plate of the sealing device according to the present invention is press-fitted into the shoulder portion of the outer joint member, so that the hub wheel, the double row rolling bearing, and the constant velocity universal joint are connected. In the wheel bearing device of the fourth generation structure unitized by plastic coupling, reassembly by means of seal entanglement is conventionally impossible. However, this radial lip is substantially completely eliminated, and such non-separation is not possible. Type 4th generation wheel axle Applying the sealing device described above to the apparatus, there is a tremendous effect in terms of assemblability well surface sealability.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an embodiment of a sealing device according to the present invention.
FIG. 2 is a longitudinal sectional view showing an embodiment of the wheel bearing device according to the present invention.
FIG. 3 is a longitudinal sectional view showing a conventional sealing device.
FIG. 4 Same as above.
[Explanation of symbols]
1, 16 ... Sealing device 2 ... Seal plate 2a ...・・・・・・・ Cylindrical part 2b ・・・・・・・・・・ Standing plate part 3 ・・・・・・... Elastic seal 4 ... Inner member 4a ... Outer diameter surface 5 Core metal 5a Cylindrical portion 5b ··················································································・・・・・・・ Side lip 6c ・・・・・・・・・ Radial lip 7 ・・・・・・・・・・Outer part 7a ········ Car body mounting flange 7b ········· Outside rolling surface 8 ···・・・・・・・ Labyrinth seal 9 ・・・・・・・・・・ Hub wheel 10 ・・・・・・・・・・········ Wheel mounting flange 11 ·································・ Double row rolling bearing 13 ・・・・・・・・・・・・ Inner member ・・・・・・・・・・・・・ Rolling element 15・・・・・・・・・・・ Cage 17 ・・・・・・・・・・・・ Constant velocity universal joint 18 ・・・・・・················································ Mouth 19a ... track groove 20 shoulder 21・・・・・・・・ Shaft part 21a ・・・・・・・ Small diameter step part 21b ・・・・・・・・・Joints 22 and 23 End caps 50 and 60 Sealing device 51 ... Inner ring 52 ... Outer ring 52a ... Width surfaces 53, 61 ... Seal plates 54, 62 ... Elastic seals 55, 63 ... .......... Cores 56, 64 ... Elastic bodies 56a, 56b, 64 a, 64b side lip 56c, 64c radial lip 61a cylindrical part 61b・・・・・・・・・・ Standing plate part 63a ・・・・・・・・・ Cylindrical part 63b ・・・・・・・・・・・・・・・・・ Side plate part 64d ・・・・・・・・・ Eave part 65 ・・・・・・・・・ Labyrinth seal H: Section height

Claims

相対回転する外方部材と内方部材の環状空間を密封する密封装置であって、固定側の外方部材に弾性シールを装着し、これに対向する断面Ｌ字状で環状のシール板を回転側の内方部材に圧入してなり、前記弾性シールは、先端に向かって径方向外方に傾斜し、かつ互いに径方向の内外に離れて設けられ、前記シール板の立板部に摺接する２枚のサイドリップと、前記内方部材の外径面に摺接するラジアルリップを有していることを特徴とする密封装置。A sealing device for sealing an annular space between an outer member and an inner member that rotate relative to each other, wherein an elastic seal is mounted on an outer member on a fixed side, and an annular seal plate having an L-shaped cross section opposed thereto is rotated. The elastic seal is inclined radially outward toward the distal end and is provided radially inward and outward, and is slidably in contact with the upright portion of the seal plate. A sealing device comprising: two side lips; and a radial lip that slides on an outer diameter surface of the inner member.

前記ラジアルリップの先端が、前記シール板の立板部と反対側に傾斜して延びている請求項１に記載の密封装置。The sealing device according to claim 1, wherein a tip of the radial lip extends obliquely to a side opposite to the upright portion of the seal plate.

前記弾性シールが、前記シール板に対向する略Ｌ字状の芯金と、この芯金に一体固着された弾性体とからなり、前記芯金の円筒部の先端部と前記シール板の立板部の先端とが僅かな径方向隙間を介して対峙するように設けられている請求項１または２に記載の密封装置。The elastic seal includes a substantially L-shaped metal core facing the seal plate, and an elastic body integrally fixed to the metal core. The sealing device according to claim 1, wherein the sealing device is provided so as to face a tip of the portion via a slight radial gap.

ハブ輪と等速自在継手と複列の転がり軸受とをユニット化し、前記ハブ輪と等速自在継手の外側継手部材とを嵌合させ、この嵌合部で、前記ハブ輪の内周面に硬化させた凹凸部を形成し、この凹凸部に前記外側継手部材の嵌合部を拡径させて食い込ませることにより、前記ハブ輪と外側継手部材とを一体に塑性結合した車輪用軸受装置において、
前記外側継手部材の肩部に請求項１乃至３いずれかに記載した密封装置のシール板を圧入したことを特徴とする車輪用軸受装置。The hub wheel, the constant velocity universal joint, and the double row rolling bearing are unitized, and the hub wheel and the outer joint member of the constant velocity universal joint are fitted to each other. A wheel bearing device in which the hub wheel and the outer joint member are plastically integrated integrally by forming a hardened uneven portion and expanding and fitting the fitting portion of the outer joint member into the uneven portion. ,
4. A bearing device for a wheel, wherein the sealing plate of the sealing device according to claim 1 is press-fitted into a shoulder of the outer joint member.

前記複列の転がり軸受における内側転走面のうち一方を前記ハブ輪に、他方を前記外側継手部材にそれぞれ形成した請求項４に記載の車輪用軸受装置。5. The wheel bearing device according to claim 4, wherein one of the inner rolling surfaces of the double row rolling bearing is formed on the hub wheel, and the other is formed on the outer joint member.